DESCRIPTION: The investigator proposes to isolate cone-specific cDNAs as a means to delineate the function of the visual cascade and cell biology of cone cells in addition to providing candidates for study of the cd dog in specific aim II. To accomplish this, the investigator will use the cd dog, the only available animal model of cone degeneration. Two techniques are proposed to identify mRNA species present in normal dogs, but absent from cd/cd dog retinas. The first is differential display of the two mRNA populations. This will be based on the use of four degenerately tailed oligo dT primers differing only in their last base and 20 10-base upstream primers. Subtractive hybridization will also be used to generate a pool of cone-specific cDNAs, the technique the investigator used to isolate the mouse rd gene. Specific Aim II. The investigator proposes to identify and characterize the gene lesion responsible for the cd dog disease. To accomplish this, differential display of retina mRNAs from pre-degenerate cd/cd and age matched normal dogs and possibly subtractive hybridization of predegenerate cd/cd retinas with age-matched cd/+ retinal cDNAwill be used. The investigator will use GDRDA if the first two techniques are unsuccessful.